This application is the national phase under 35 U.S.C. xc2xa7 371 of PCT International Application No. PCT/JP02/05317 which has an International filing date of May 30, 2002, which designated the United States of America.
The present invention relates to a multilayered spectroscopic device for use in fluorescent X-ray analysis of boron, of a kind wherein a plurality of layer pairs each pair including a reflecting layer and a spacer layer are laminated on a substrate.
As a spectroscopic device for B-Kxcex1 line (Wavelength: 6.76 nm) during fluorescent X-ray analysis of boron, the multilayered spectroscopic device has hitherto been known in which reflecting layers are made of molybdenum (Mo) and spacer layers are made of boron carbide (B4C). However, to achieve a highly accurate fluorescent X-ray analysis of boron in a short length of time, with the Mo/B4C based multilayered spectroscopic device B-Kxcex1 line do not give rise to a sufficient strength of reflection and neither interfering X-rays such as the third-order reflection of O-K line nor background such as Si-L line can be suppressed sufficiently. In contrast thereto, the published International Application WO 00/75646 A2 addresses that if lanthanum (La) and boron carbide are used for each of the reflecting layers of the multilayered spectroscopic device and for each of the spacer layers of the same multilayered spectroscopic device, respectively, the strength of reflection of B-Kxcex1 line can be increased as compared with that exhibited by the Mo/B4C based spectroscopic device. Also, it is known that the theoretical calculation has revealed that the use of lanthanum and boron for the reflecting and spacer layers of the multilayered spectroscopic device is effective to increase the strength of reflection of B-Kxcex1 line can be increased as compared with that exhibited by the Mo/B4C based spectroscopic device.
However, even with the La/B4C based multilayered spectroscopic device, the strength of reflection of B-Kxcex1 line is still insufficient in order to achieve in a short length of time the highly accurate fluorescent X-ray analysis of boron. Also, with respect to the La/B based multilayered spectroscopic device, it is only known from the theoretical calculation that as compared with the Mo/B4C based multilayered spectroscopic device the strength of reflection of B-Kxcex1 line can be increased, and it has been difficult to manufacture the multilayered spectroscopic device by finding specific conditions under which the strength of reflection of B-Kxcex1 line can be sufficiently increased and, at the same time, reducing any possible influence brought about by the interfering X-rays and the background.
The present invention has been devised with a view to the foregoing problems and is intended to provide a multilayered spectroscopic device effective to achieve in a short length of time the highly accurate fluorescent X-ray analysis of boron wherein the influence that may be brought about by the interfering X-rays and the background is sufficiently reduced and the strength of reflection of B-Kxcex1 line is sufficient.
In order to accomplish the above described object, the present invention provides a multilayered spectroscopic device utilizable in fluorescent X-ray analysis of boron contained in a sample and including a substrate on which a plurality of layer pairs each pair including a reflecting layer and a spacer layer are laminated, wherein lanthanum (La), an alloy containing lanthanum as a principal component or lanthanum oxide (La2O3) is used for each of the reflecting layers and boron is used for each of the spacer layers, a periodic length is within the range of 7 to 14 nm and a film thickness ratio of the reflecting layers to the spacer layers is within the range of 2/3 to 3/2, and wherein the multilayered spectroscopic device has a total laminated film thickness sufficient to allow a strength of reflection of B-Kxcex1 line to attain a value equal to or higher than 98% of a saturation value.
With this structure, as compared with the conventional Mo/B4C based multilayered spectroscopic device it is possible to increase the strength of reflection of B-Kxcex1 line by a factor of about 2.2 to 3.8 while the influence brought about by the interfering X-rays such as third-order reflection of O-K line and the background such as Si-L line can be sufficiently reduced and, on the other hand, as compared with the conventional La/B4C based multilayered spectroscopic device it is possible to increase the strength of reflection of B-Kxcex1 line by a factor of about 1.3 and, accordingly, it is possible to accomplish the fluorescent X-ray analysis of boron highly accurately in a short length of time. Preferably, the total laminated film thickness is within the range of 280 to 320 nm and the film thickness ratio of the reflecting layers relative to the spacer layers is preferably about equal to 1 and within the range of 4/5 to 5/4.